The present invention relates generally to a clutch plate for a friction clutch.
The clutch plate comprises a friction disc carrying friction facings and a hub mounted for angular movement relative to each other within a predetermined range of angular displacement. The support member and the hub are coupled together by staged torsion damping means. The staged torsion damping means comprises a first, low-rated torsion damping means and a second, stiffer torsion damping means, each of the first and second stage damping means comprising a radial flange, two guide washers fixed to each other and disposed on axially opposite sides of the flange. Resilient means are interposed circumferentially between the flange and the guide washers. The first stage damping means is adapted to operate between the hub and the second stage damping means. The flange of the second stage is mounted with angular clearance on the hub whereas the friction disc is fixed to one of the guide washers of the second stage damping means.
The second stage damping means may also be staged and comprises resilient members of different stiffness operable in succession ; it has the main damping function during normal operation when the variable torque is transmitted by the friction disc, in either direction and thus operates to filter vibrations particularly in the case of use in a motor vahicle.
The second stage damping means, despite its efficacy in normal operating conditions, is found to be insufficient to efficiently absorb vibrations when the torque transmitted by the friction disc is very low or nil, such as found when a motor vehicle idles; in this mode of operation the second torsion stage is incapable of preventing the noises known as dead point or idling noises from developing.
That is the reason why the first stage torsion damping means operates as a pre-damper specially adapted for damping vibrations and noises in particular operation conditions in which the torque transmitted is very low, notably when the vehicle is idling.
Conventionally in friction clutch plates of the foregoing type, the flange of the first stage damping means is fixed for rotation with the hub whereas the washers of the first stage damping means are fixed to the second stage damping means.
Generally, in known constructions the assembling is complicated and has special requirements.
Further, the bulk is often considerable and mechanical strength is insufficient.